It is part of the general state of the art that material fired in a rotary kiln is passed via a stationary kiln outlet head associated with the outlet end of the rotating cylinder and an inlet shaft positioned below it to a cooler arranged after the rotary kiln. One end of the stationary kiln outlet head surrounds the edge region of the end of the rotating cylinder facing it to a sufficient extent to ensure adequate sealing in this region. At the connection point between this kiln outlet head and the inlet shaft a sealable separating gap is provided in such a way that alterations in the length of the kiln attributable to the effects of temperature and resulting displacement of the kiln outlet head can be largely accommodated.
In such a rotary kiln and cooler assembly it must be ensured that the shortest possible drop is maintained for the material falling from the end of the rotating cylinder into the cooler. This is on the one hand because with a relatively long drop the dust pollution in the air rising in counterflow to the fired material is undesirably high (excessive dust pollution in the firing process or in the associated dust separators), and on the other hand because the fired material frequently falls out of the end of the rotating cylinder in relatively large and heavy lumps and can lead to considerable mechanical stress on impact with the cooling equipment. Although in the case of rotary kilns with relatively small dimensions the drop height for the fired material generally remains within acceptable limits and the separating gap to be sealed between the kiln outlet head and the cooler inlet shaft can be arranged to run approximately horizontally (so that as a rule sufficient movability of the kiln outlet head can be ensured during operation), in the case of larger rotary kilns considerable problems frequently occur in maintaining the acceptable drop height for the fired material. In order to keep this drop height as small as possible, in the case of larger rotary kilns there has been a changeover in practice to constructing the separating gap at the connection point between the kiln outlet head and the inlet shaft so that it runs at an angle, and as a result the end of the inlet shaft opposed to the outlet end of the rotating cylinder is correspondingly higher and the appertaining end wall of the kiln outlet head is correspondingly lower so that the drop height can be kept relatively small. However, this inclined separating gap only permits a very restricted movability of the kiln outlet head in the longitudinal direction of the kiln, which brings certain disadvantages with it: if the rotating cylinder is excessively elongated (due to heating) sufficient compensation therefor cannot always be ensured with the necessary reliability by the movability of the head, and attention must be paid to ensure that the inclined separating gap which has to accommodate the longitudinal expansion of the kiln during the compensation must at the same time seal the connection point between the kiln outlet head and the inlet shaft and therefore must not be excessively large, although on the other hand if it is not wide enough it can restrict the possibility of longitudinal expansion or compensation therefor by the kiln outlet head; because of this limited movability of the kiln outlet head the collar thereof which engages over the end of the rotating cylinder must be capable of being dismantled in sections so that the relevant end of the rotating cylinder is accessible for maintenance work.
An object of the invention, therefore, is to construct a rotary kiln of the type referred to and in which the transitional region to its cooler enables, in a simple manner, a relatively small drop height for the fired material to be maintained even with larger kiln dimensions and sufficient movability of the kiln outlet head.